Method of forming an impermeable wall in the terrain



1mg. 7, 1956 H. T. WYATT 2,757,514

METHOD OF FORMING AN IMPERMEABLE WALL IN THE TERRAIN Filed July 16, 1951 INVENTOR. #49010 7- 41/7477 United States Patent METHOD OF FORMING AN Ill/[PERMEABLE WALL IN THE TERRAIN Harold T. Wyatt, Arcadia, Califi, assignor to Cronese Products, Inc., a corporation of California Application July 16, 1951, Serial No. 237,003

Claims. (Cl. 61-31) This invention relates to a method of providing an impermeable cut-oif wall or barrier in the terrain, in a dike, earthwork, embankment or the like to prevent the passage of Water or the like through subterranean strata.

In the above identified co-pending application, the method disclosed therein of forming a cut-01f wall included the steps of excavating to form a trench, filling the trench with a moistened clay, and, while forming the trench, keeping it filled with a colloidal mud to prevent the side walls of the trench from caving in or collapsing without the use of timbering, cribbing or the like. The excavated material in my prior method was discarded and not utilized.

A main object of the present invention is to provide a method of forming a cut-off wall in the terrain which method includes the steps of utilizing the excavated material by mixing the excavated material With a colloidal mud to replace the water, air and like substances in the pores of the excavated material with mud, and filling the trench with such mixture to form an impermeable wall in the terrain.

Another primary object of the present invention is to provide a method of forming a cut-off wall utilizing a mixture as set out above and by which the trench is maintained full of a colloidal mud during the excavation to prevent caving and collapsing of the walls of the trench.

A further object of the present invention is to provide a method for forming a cut-off wall, which method ineludes the steps of continuously excavating material to form a trench, mixing the material with a colloidal mud, and returning the material to the trench so that a cutoff wall is formed in a progressive manner.

A still further object of the present invention is to provide a method of forming a cut-ofi wall in a section of earth containing a stratum of clay useful as a constituent in a mixture for forming an impermeable wall, which method includes the steps of excavating down to a depth to at least partially, and preferably entirely, include the clay stratum, mixing the excavated material including the clay, preferably in the presence of water, and filling the trench with such mixture to form an impermeable cut-off wall. Where the clay in the stratum is not sufiicient to provide the degree of impermeability desired the method just described may also include the step of supplementing the natural clay with a colloidal clay or mud to obtain the desired degree of impermeability of the wall.

Various other objects of the present invention will be apparent from the following description taken in connection with the accompanying drawings, wherein:

Fig. 1 shows a dragline excavator forming an initial trench or bell-hole in the terrain.

Fig. 2 shows the dragline excavator with the bucket thereof in the process of dumping a load of a mixture of earth and colloidal mud at the rear end of the initial trench or bell-hole.

Fig. 3 shows the dragline bucket being dragged up the forward end of the trench and removing earth in the presence of the colloidal mud.

Fig. 4 shows a screening device alongside the trench in a position to receive a mixture of mud and excavated material from the dragline excavator and return mixed material to the trench.

The drawings illustrate various steps in the formation of an impermeable cut-off wall in the terrain and illustrate a dragline excavator useful in carrying out the steps. These illustrations are not intended to limit the invention but merely to illustrate a specific application of the method of the present invention.

In its broadest aspect, the present invention comprises the steps of replacing permeable sediments in the terrain with a mixture of permeable sediments and a colloidal mud. Preferably, the operation of forming a cutoff wall is a continuous one in which the terrain is progressively excavated, and the excavated material mixed with a collodial mud as it is excavated and returned to the trench to fill the trench. Also it is preferable that the trench be filled with a colloidal mud during the trenching and back-filling operations so as to provide a convenient supply of mud for mixing purposes, to retain the walls of the trench in place and prevent caving or collapsing thereof, and to serve as a replacement material. Additional colloidal mud is added to the trench at intervals or continuously, as desired, to replace the mud used in the mixture.

Where there is a stratum of clay in the earth, the method of the present invention provides a convenient way of forming a cut-off wall in the terrain. For example, the earth in a river bank may consist of clear, permeable gravel overlain by a layer of useful clay, perhaps separated by layers of sand and gravel. The earth is excavated along the line of formation of the trench and down to a depth to at least partially and preferably entirely include the clay stratum, the excavating process preferably taking place in the present of water or a colloidal mud. If the clay in the stratum is of a sufficient amount, the excavated material including the clay can be mixed in the present of water and returned to the trench. The mixture will consist of a colloidal mud (the combination of clay and water and the earth, and therefore segregation of the fine and coarse materials will be avoided. Where the natural clays are not sufiicient to form the required degree of impermeability of the resulting cut-ofi wall, colloidal mud is added as required to supplement the natural clays to thereby fill the pores of the permeable sediments and effect the desired degree of impermeability. Where the ground formation is weak and cavy, the particular steps above described are preferably carried out with the trench filled with a colloidal mud rather than water since the colloidal mud is more effective to retain the walls in place.

Referring to the drawings, there is disclosed a drag line excavator for forming a cut-off wall in the terrain in what may be termed a continuous fashion. The dragline excavator generally designated by the reference numeral it) includes a boom 11, a bucket 12 and a dragline 13. An initial trench or bell-hole 15 is formed in the terrain in the presence of a colloidal mud. 16, which is supplied to the trench, as the excavation proceeds, to maintain the trench full of this colloidal mud. There is no backfilling during the formation of this initial trench or bell-hole. The excavation continues until the bellhole has been excavated to a depth substantially equal to the depth of the cut-off wall to be formed in the terrain. The colloidal mud during these excavating operations prevents the walls of the trench or bell-hole from caving in or collapsing.

Fig. 1 depicts the bucket 12 as being dragged along the bottom of the trench 15 and in the act of completing the formation of the initial trench or bell-hole. At this point in the excavation, the formation of the impermeable wall is begun by scraping or removing material from the forward end, which is the lefthand end of the trench as the parts are depicted in the drawing, in the presence of the colloidal mud 16, as shown in Fig. 3, and dumping the mixture of excavated material and colloidal mud at the rear end of the trench, as shown in Fig. 2. The cut-off wall, a part of which is shown in Figs. 3 and 4, and designated by the reference numeral 21, is formed by successive cycles of operations of dragging the bucket across the forward end of the trench, excavating material in the presence of mud 16 to mix the mud with the material and replace the air and water in the pores of the material with the colloidal mud, and dumping the mixture at the rear end of the trench.

During the extension of the trench, the dragline excavator progresses along the line of formation of the trench and additional mud is supplied to the trench to replace the mud used in the formation of the impermeable cut-off Wall 21.

As shown in Fig. 4, a mobile screening mill 23 may be provided adjacent the trench to screen the excavated material and remove some of the excavated material, such as boulders, or some of the liquid mud, before returning the excavated material to the trench. The arrangement shown in Fig. 4 is one where only boulders or the like are being separated and the balance of the mixture is being returned through a chute 24 to the trench to fill the trench. If part of the colloidal mud is to be removed by the mobile screening mill, another chute or conduit may be provided for conducting this mud back to the trench at a point forwardly of chute 24. As the trench is filled, the mobile screening mill 23 will be moved forwardly alongside the trench to progressively fill the trench.

Although a dragline excavator and a mobile screening mill have been shown in the drawings, it is obvious that other types of equipment and apparatus could be used in carrying out the steps of the present invention. For instance, other types of dredging machines, ditch digging machines, clam shell shovels and hoes could be used. Instead of a mobile screening mill, a stationary screening mill could be provided, having a mobile conveyor extending therefrom with the outer end of the conveyor being moved along the trench during the filling thereof.

In Fig. 4, the stratum of clay 25 has been shown in the terrain at the forward end of the trench to illustrate the usual location of a trench with reference to a stratum of clay.

Although the method of the present invention has been described particularly with reference to forming a cut-off wall in the terrain, it is obvious that the invention is not so limited, and the method of the present invention can be used for forming a cut-off wall in embankments, dikes, along shore lines, and the like.

By the present invention, a method of forming an impermeable cut-ofi wall in the terrain has been provided which utilizes the excavated material by mixing the material with a colloidal mud and returning the mixture to the excavation to form an impermeable wall. By such an impermeable wall, the passage of water through subterranean strata or through other sections of the earth can be prevented.

The method of the present invention can also be used for constructing a trench across the bottom of a river, into which trench tunnel sections are lowered, thus providing an under-river tunnel by a simple dredging operation rather than by the expensive boring method commonly used. As the trench is formed under water, it is kept filled with a colloidal liquid mud which is weighted with material such as hematite or barite. The Weighting assures that the colloidal liquid will remain in the trench while the river flows over the top. The colloidal liquid has a restraining effect on the walls of the trench to prevent caving in of said walls where the river bottom is of a soft or slimy nature.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. A method of forming a flexible impermeable cut-01f wall in terrain comprising forming a bell-hole in the terrain, filling the bell-hole with a colloidal mud during the formation thereof, removing earth from one end of the bell-hole in the presence of the mud and depositing the resulting mixture of earth and colloidal mud in the bell-hole at the other end thereof, and continuing the last named operation to form a wall composed of a mixture of earth and mud.

2. The method of forming a flexible impermeable wall in terrain having boulders therein, comprising forming a bell-hole in the terrain, filling the bell-hole with a colloidal mud, removing earth material and boulders from one end of the bell-hole in the presence of the mud to form a mixture therewith, separating boulders from the material and depositing the balance of the material in the bell-hole at the other end thereof.

3. The method of forming an impermeable cut-off wall in terrain comprising providing a dragline excavator, positioning the excavator at one end of a line along which an impermeable wall is to be formed in the terrain, operating the dragline excavator to form a bell-hole in the terrain,

filling the bell-hole with a colloidal mud during the excavation thereof, operating the dragline apparatus so as to remove earth from the bell-hole at one end thereof in the presence of the mud to mix the earth and mud and to deposit the mixture in the bell-hole at the opposite end thereof, and continuing the last mentioned operations while operating the dragline apparatus so that it moves down the line along which the wall is to be formed.

4. The method of forming an impermeable cut-off wall in the earth to stop the passage of water through subterranean strata, comprising: forming a length of trench by excavating along a line along which the wall is to be formed; substantially filling such length of trench with colloidal mud to support the walls thereof; continuing the excavation procedure by removing earth material submerged in said colloidal mud from one end portion of the trench to obtain a mixture of earth material and colloidal mud; depositing the mixture in the opposite end portion of the length of trench; and replenishing the supply of colloidal mud to maintain such length of trench substantially filled.

5. The method of forming an impermeable wall in a section of earth which section includes a stratum of clay, comprising: excavating a length of trench along a line along which the wall is to be formed and to a depth to at least partially include such clay stratum; substantially filling said length of trench with colloidal mud to support the walls thereof; continuing the excavation procedure by removing earth material submerged in said colloidal mud from one end portion of the length of trench to obtain a mixture of earth material, including clay, and colloidal mud; depositing the mixture in the opposite end portion of the length of trench; and replenishing the supply of colloidal mud to maintain such length of trench substantially filled.

References Cited in the file of this patent UNITED STATES PATENTS 922,207 Strauss May 18, 1909 1,441,308 Tappan Jan. 9,- 1923 1,547,341 Meem July 28, 1925 2,038,160 Billings Apr. 21, 1936 2,139,929 Blow Dec. 13, 1938 2,154,233 Donaldson Apr. 11, 1939 OTHER REFERENCES Engineering News Record of January 19, 1939-pages 63-64. 

